Conventionally, there are various methods as a communication method that is used for the data transmission and reception of a communication device such as a mobile terminal or a base station. For example, a communication method includes LTE (Long Term Evolution), HSPA+ (High Speed Packet Access+), and the like. Moreover, a communication device that uses LTE and HSPA+ uses a turbo code as an error correction code.
A communication device that uses a turbo code executes an interleaving process and a de-interleaving process in the process of decoding a signal encoded with the turbo code. In this case, an interleaving process is a process for rearranging the order of signals that are stored in a memory. Moreover, a de-interleaving process is a process for restoring the order of signals that are rearranged by the interleaving process.
It is further explained about an example of a turbo decoding process for decoding a signal encoded with a turbo code. For example, a communication device executes, when receiving a signal (A), a decoding process on the received signal (A) and stores its result in a memory. Then, the communication device executes an interleaving process on the signal (A), executes a decoding process on a signal (b) after the interleaving process, and again stores its result in the memory. Then, the communication device executes a de-interleaving process on the signal (B), executes a decoding process on a signal (C) after the de-interleaving process, and stores its result in the memory once more. In this case, the order of the signal (A) and signal (C) is the same.
In this case, the processing methods of an interleaving process and a de-interleaving process are different depending on the coding methods of a turbo code. Moreover, the coding methods of a turbo code are different depending on communication methods. For this reason, for example, LTE and HSPA+ execute different interleaving process and de-interleaving process. For example, a communication device that uses LTE uses “QPP (Quadratic Permutation Polynomial Interleaver)”. On the other hand, a communication device that uses HSPA+ uses “PIL (Prunable Prime Interleaver)”.
When executing a turbo decoding process, there is a communication device that executes a decoding process in parallel by performing reading and writing on a plurality of memories in parallel. For example, the communication device divides a signal into a plurality of signals and concurrently executes a decoding process on the divided signals. In this case, the capacity of each memory and the number of memories mounted on the communication device that concurrently executes the decoding process are different depending on the maximum size of a signal, the processing methods of an interleaving process and a de-interleaving process, the number of processes that are concurrently executed by the communication device, and the like.
For example, because the maximum sizes of a signal in LTE and HSPA+ are different, memories mounted on a communication device that uses LTE and memories mounted on a communication device that uses HSPA+ are different from each other in terms of the capacity of each memory and the number of memories. The technique has been known as disclosed in, for example, Japanese Laid-open Patent Publication Nos. 2008-135813, 2008-219892 and 2008-118628 and International Publication No. WO 2006/082923.
It is desired that a communication device that concurrently executes a decoding process corresponds to a plurality of communication methods. Moreover, it is demanded that the communication device corresponds to turbo decoding processes that are used for the communication methods after corresponding to the plurality of communication methods. Considering that the capacity and number of memories mounted on the communication device that concurrently executes the decoding process are different depending on communication methods, it is required a mounting device that mounts thereon separate memories depending on communication methods.
For example, when a communication device corresponding to both of LTE and HSPA+ is realized, a mounting device separately mounts memories that are used for executing a turbo decoding process by using LTE and memories that are used for executing a turbo decoding process by using HSPA+.
However, there is a problem in that the mounting device separately mounts memories depending on communication methods and thus the burden of memory increases.